Acyclic generator with vacuum arc commutator for rapid generation of short, high-energy pulses

ABSTRACT

Short pulses of high energy are generated at a high-pulse rate by providing high energy from an acyclic generator having a plurality of discs rotating in the field of a superconductive field coil and commutating the output of the generator, through an electric discharge device connected across the same, by means of a pair of oppositely poled, sequentially operated triggerable vacuum arc devices.

United States Patent Swartz et a1.

[54] ACYCLIC GENERATOR WITH VACUUM ARC COMMUTATOR FOR RAPID GENERATIONOF SHORT, HIGH-ENERGY PULSES Paul S. Swartz; Willem both of Schenectady,N.Y.

General Electric Company NOV. 19, 1970 Inventors:

[ F. Westendorp,

Asslgnce:

Filed:

Appl. No:

US. Cl. ..3l5/205, 310/126, 310/148, 310/178, 310/268, 315/226, 315/240,315/330 Int. Cl. ..ll02k 29/02, H021: 31/02, l-l05b 41/34 Field 01Search ..315/200 A, 205, 226, 240, 330; 310/126, 148,178,268

[56] References Cited UNITED STATES PATENTS 3 g,g7o 302% 13 3 115..315/240 x 51 Feb.29,1972

3,443,134 5/1969 Dowsett et al ....3 10/178 3,497,739 2/1970 Appleton..3 l0/ 1 78 3,586,894 6/1971 Mueller ..3 10/178 Primary Examiner-RobertSegal Assistant Examiner-Siegfried H. Grimm Altomey-Jo1m F. Ahem, PaulA. Frank, Richard R. Brainard, Jerome Sqidllaro, Frank L. Neuimmer,Oscar B Waddellandlosqah B. Form [57] ABSTRACT Short pulses of highenergy are generated at a high-pulse rate by providing high energy froman acyclic generator having a plurality of discs rotating in the fieldof a superconductive 'field coil and commutating the output of thegenerator,

through an electric discharge device connected across the same, by meansof a pair of oppositely poled, sequentially operated triggerable vacuumarc devices.

13 Claims, 2 Drawing Figures ACYCLIC GENERATOR WITH VACUUM ARCCOMMUTATOR FOR RAPID GENERATION OF SHORT, HIGH-ENERGY PULSES The presentinvention relates to apparatus and methods of generating short pulses ofhigh energy. More particularly, the invention is directed to therepetitive production and utilization of such pulses without thelimitations imposed by conventional energy generating and switchingmeans of the prior art.

In the electrical arts, there are many instances in which short,high-energy pulses of electric power are required. Such uses include theproduction of power supplies for high-power electron devices, for radiotransmitters, radio telescopes and the like. Similarly, the illuminationarts require high-energy sources for many specialized uses such as forhigh-power flash lamps, for photography, and for visual navigation aidssuch as, for example, beacons and light ships.

There are many problems associated with presently available high'energysources, such as capacitors, inductive reactors, and the like,Generally, such reactances capable of producing high-energy pulses arevery cumbersome and are heavy and occupy a large amount of space.Another problem, generally found in high-energy reactors, is that onceenergy has been supplied thereto, getting energy therefrom involves anintricate, so far, insoluble switching problem. Due to the problems ofswitching, the speed with which such devices may be operated isrelatively limited and, in addition to the energy lost in switching,there is a limitation upon frequency of operation which cannot beexceeded. Generally, as the speed of the pulse rate required by theapplication increases, such problems also increase, rendering theproduction of highenergy, high pulse rate energy sources of the priorart totally unsatisfactory.

Accordingly, it is an object of the invention to provide apparatus andmethods for producing and switching high-energy electrical pulses at arapid pulse rate with a minimum of difficulty and with simplicity andminimal losses.

Another object of the invention is to provide apparatus and methods forproducing pulsed high-energy electric signals without mechanicalswitching thereof.

Still another object of the invention is to provide for highenergy,high-speed excitation of electric discharge lamps.

Briefly stated, in accord with one embodiment of the present invention,the foregoing objectives are-achieved by providing a high-energy sourcein the form of an acyclic generator utilizing a superconductive fieldcoil. The high energy of the acyclic generator is commutated through aload device such as an electric discharge flash lamp which is connectedthereacross, by an array of oppositely poled, parallel connected,triggerable vacuum are devices in series circuit with the load. Thecommutation of the high-energy source is accomplished by electron meansin the substantial absence of mechanical switching, particularly of highcurrents and voltages, and may be done with substantially no energylosses and with very high speed.

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, together withfurther objects and advantages thereof, may best be understood byreferring to the following detailed description, taken in connectionwith the attached drawings in which:

FIG. 1 is a schematic illustration of apparatus for producing rapidlypulsed high energy according to the invention and including an acyclicgenerator, and,

FIG. 2 is a partial vertical cross-sectional view, with parts brokenaway, of one current generating disc of an acyclic generator,illustrated schematically in FIG. 1.

In FIG. 1, the invention is illustrated schematically as including anacyclic generator represented generally at with a commutation circuit 20and a load circuit 21 connected across the output thereof. Acyclicgenerator 10 comprises a superconductive field coil 11 contained inthermal isolation means represented by dotted line boxes 12 surroundingthe constituents thereof and generally including a dewar arrangement ofthermal containers for containing liquid helium at a temperature of 41K. absolute. At such temperature, the resistance of the material fromwhich the superconductive coil is wound, generally Nb Sn, NbTi or, sucha type II superconductive material, falls essentially to zero andconductivity without resistance is obtained, thus making possible theattainment of exceedingly high-current densities, and consequently,highflux densities with a moderate voltage supply. An acyclic generatorwith a superconductive field coil is described, for example, in U.S.Pat. No. 3,443,134.

A rotor assembly 13 is located within field coil 11. Rotor assembly 13includes a first bank 14 of a plurality of rotatable discs 15, each ofwhich is capable of producing a very high current under the influence ofthe field of field coil 11. First bank 14 of discs 15 is adapted torotate in a first direction, say clockwise. A second bank 16 of aplurality of discs 15 equal in number to the number of discs 15 in bank14, are adapted to rotate in an opposite direction, say,counterclockwise. Discs 15 of bank 14 are mounted upon a torque shaft 17and are connected to a first motive means 18 which may, for example,comprise a gas turbine or other highspeed source of rotational motivepower. Similarly, bank 16 of discs 15 are mounted upon a second torqueshaft 17 and are adapted to rotate in an opposite direction, moved by asecond source 19 of rotational motive power, which may be a similardevice to motive means 18. All of discs 15 are connected electrically inseries by a plurality of brushes (not shown) and the output thereof isapplied to the commutation circuit 20 and load circuit 21 in seriesrelationship.

The commutation and load circuits in essence, comprise a pair ofparallel connected triggerable vacuum are devices 22 and 23, preferablytriggerable vacuum gap devices, and an electric discharge device, forexample, represented generally by electric discharge lamp 27, in seriescircuit arrangement. More specifically, first triggerable vacuum gapdevice 22 is in series with lamp 27 and second triggerable vacuum gapdevice 23 is in series circuit with a capacitor 24, both of which are inparallel circuit relationship with triggerable vacuum gap device 22. Apreionizing source of electric potential, represented schematically bygenerator 28, is disposed across lamp 27 to provide for a level ofionization such as to render the environment within lamp 27 electricallyconductive prior to the commutation of the high-energy therethrough.Commutation means 20, in addition to triggerable vacuum gaps 22 and 23and capacitor 24, includes a pulse and control means which mayconveniently include a highfrequency oscillator or generator of a squarewave or sawtooth wave of voltage and switching means for switching asufficiently high-voltage triggering pulse, which may be from severalhundred to several thousand volts, sufficient to cause triggerablevacuum gap devices 22 and 23 to fire at predetermined and sequentialtimes in the operation of the commutation system. Charging means 26 isprovided in parallel with capacitor 24 and need only be a simple voltagegenerator, as for example, a battery or other suitable means forimposing a unidirectional potential across capacitor 24 at apredetermined time in sequence with the pulse and control means 25.Triggerable vacuum gap devices 22 and 23 should be identical and may,for example, be triggered vacuum gaps such as that disclosed and claimedin Lafferty U.S. Pat. No. 3,087,092.

In the operation of the system as illustrated in FIG. 1, thesuperconductive field coil is properly cooled and the acyclic generatoris caused to be operative by applying actuating voltages to the fieldcoil and causing the motive means 18 and 19 to be operative to rotatebanks 14 and 16 of discs 15 in respective clockwise and counterclockwisedirections, or vice versa. The generator remains in operation throughoutthe switching cycles. The sequence of operation during switching iscontrolled by pulse and control means 25. PUlse and control means 25, inaddition to sources for generating and means for switching theappropriate voltages to cause actuation of triggerable vacuum gapdevices 22 and 23, for charging capacitor 24 and for operation ofpreionizing means 28, may conveniently include a suitably programmablecontrol means as for example, an information and storage device such asa digital computer for insuring proper and sequential operation 'of thevarious components, as described below.

The following sequence of operation is followed in accord with thepresent invention: preionizing means 28 is actuated. Capacitor 24 hasbeen previously charged from means 26. Preionization means 28 isactuated to cause a condition of preionization of the environment withinlamp 27. While this condition of preionization exists, means 25 causes apulse of triggering voltage to be supplied to triggerable vacuum gapdevice 22, providing a conductive path through lamp 27 between theoutput terminals of the acyclic generator. An exceedingly high-current,high-voltage pulse representing the full output of the acyclicgenerator, limited only by the vacuum gap, lamp, and connectionimpedances momentarily flows through device 22 and lamp 27, causing theinitiation of an exceedingly bright pulse of light from lamp 27. Uponthe initiation of the pulse to trigger vacuum gap device 22, thepreionization means 28 is deenergized.

The next step, is the controlled discharge of capacitor 24. The polarityof the voltage with which capacitor 24 is charged is such as will cause,upon the discharge thereof through triggerable vacuum gap device 22, acurrent which is of opposite direction to the current through the mainline between the output terminals of the acyclic generator.Approximately one pulse width after firing of gap device 22, pulse andcontrol means 25 transmits a suitable pulse of voltage to triggerablevacuum gap 23 to cause it to become conductive. Capacitor 24 dischargesthrough triggerable vacuum gap device 23 and the discharge current loop,including both gap devices, causes a current through triggerable vacuumgap device 22 which exactly neutralizes the current from the generator,causing zero net current through triggerable gap device 22, whichdeionizes and becomes nonconductive. The current through the lamp is notextinguished immediately, however, because the main current fromgenerator passes momentarily through the ionized triggerable vacuum gapdevice 23, which is still ionized, for a sufficient period of time toreverse the charge of capacitor 24. Upon the reverse charging ofcapacitor 24 to its maximum charge through triggerable vacuum gap device23, current through the lamp 27 is terminated, and one cycle has beencompleted. Gap device 23 is then deionized and becomes nonconductive.Upon the completion of the cycle, the program begins once again afterrecharging of the capacitors, with preionization of the lamp, firing ofthe first triggerable vacuum gap to initiate a pulse and firing of thesecond triggerable vacuum gap device to terminate a pulse.

Since all of the operations in the foregoing sequence are conductedwithout mechanical switching of any high current or high voltage, butonly of triggering or control voltages, which may also be doneelectronically with solid-state devices, the system of FIG. 1 mayoperate at very high speed and without losses or deterioration ofelectrodes or the like.

Assuming that the plurality of current generating discs are eachrequired to produce a voltage of at least 500 volts, this may beaccomplished utilizing individual discs of approximately 24 inches indiameter, since a field of approximately'80 kilogauss at a rotationalspeed of 19,100 r.p.m. is sufficient to provide the necessaryinteraction to produce such voltage. A single pulse of approximately4,000 volts at 100,000 amperes for approximately 250 microsecondsremoves approximately 100,000 joules from the generator. This imposes asevere mechanical stress upon the acyclic generator. Additionally, themere rotation of the rather massive discs upon the shaft also imposessevere mechanical strain and causes gyroscopic forces, unlessneutralized. It is for this reason that half the individual discs 15 aremounted on one torque shaft and rotate in a first direction while theother half of the discs 15 are mounted upon a second torque shaft androtate in an opposite direction. This eliminates the gyroscopic forcesand also tends to minimize the mechanical stress when a very largeamount of energy is extracted from the generator. The structure of thegenerator must nevertheless, be carefully designed to compensate for thetorques and forces attendant such extraction.

FIG. 2 of the drawings illustrate a partial cross-sectional view of aportion of the torque assembly of the acyclic generator of FIG. 1 whichshows the manner in which such torques may be handled. In FIG. 2, a pairof discs 30 and 31 having large central thicknesses and reducedperipheral thicknesses wherein the taper may, for example, be limited tothe external 60 percent of the diameter thereof and may be along inversehyperbolic curves, are mounted upon torque shaft 32. Mounting of thediscs upon the torque shaft is not rigid, but is accomplished, forexample, by a pair of splined rings 33 and 34 at either end of disc 30rigidly interconnected with the slots 35 in shaft 32 and mechanicallybound, in axially slippable connection, with disc 30 by means of springpressure applied by springs 36 against pressure plate 37 from springmount 38. An insulator 39 completely surrounds the periphery of theinternal portion of disc 30 in the vicinity of the mounting arrangement.

When an energy containing pulse is extracted from the generator,assuming the discs weigh kilograms each and have a total kinetic energyof 64,000,000 joules, the extraction of 100,000 joules causes a decreasein rotational velocity of l/1280th in 250 microseconds. Although this isa relatively small change in velocity, sufficient slippage must bepermitted so that the torque may be absorbed by the machine. This isadequately provided by the spring pressure between the splined discs onthe splined shaft and the slippable charge generating discs 30 and 31,as illustrated herein.

Energy is extracted from the discs by means of brushes 40 and 41 whichserially connect discs 30 and 31 through brush holder 42. Means areprovided to supply pressure to the brushes only during that portion ofthe operating cycle in which the energy is being extracted. Such meansmay conveniently be a pressure actuating system which is sequentiallycontrolled by pulse and control means 25.

The discs 30 and 31 may conveniently be fabricated from a berylliumalloy or a special alloy steel which has the mechanical strength towithstand the tensile stresses generated by rotation at approximately19,000 to 20,000 r.p.m. Thus, assuming an angular velocity of 2,000radians per second, the tensile strength required may be between 100,000and 200,000 psi. The pulsed torque reaction during the generation ofhighenergy pulses in accord with the invention may cause the existenceof torques of approximately 800 times the average torque of the motivemeans to exist within the mechanical portion of the acyclic generatorduring operation. As is men tioned hereinbefore, a device having thedimensions illustrated herein may, utilizing eight discs in series,generate 4,000 volts, 100,000 ampere pulses of 250 microseconds with apulse repetition rate of approximately 5 pulses per second for up to 10minutes of operation, without seriously causing detrimental effects toany of the constituents of the system.

No torque is imposed upon the superconductive coil during operation. Thetorques generated in the rotating parts of the acyclic generator arecounteracted by torques upon the stationarybrush support cylinder 42 andits mounting cylinder 43. Cylinder 43 is in mechanical contact with allstationary stationary discs 42 but is electrically isolated therefrom byinsulator 44.

By the foregoing, we have disclosed an improved system and method forthe generation of high-energy pulses of electric energy at very highspeeds and for very short time duration for the operation of electrical,electronic and illuminating devices. Very high-voltages and veryhigh-currents for very short periods of time may be generated andswitched due to the absence of all mechanical switching at high voltageand/or high currents and complete control of the sequence of operation.

While the invention has been set forth herein with respect to certainspecific examples and particular embodiments, many modifications andchanges will immediately occur to those skilled in the art.Accordingly,,we intend by the appended claims, to cover all suchmodifications and changes as fall within the true spirit and scope ofthe foregoing disclosure.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. Apparatus for repetitively producing high-energy electric pulses ofvery short time duration and comprising:

a. an acyclic generator adapted to generate and transfer a charge of1,000 joules of energy;

b. an electric discharge load device switchably connected across theoutput of said acyclic generator;

c. means in circuit with said load device for preionizing said device torender it electrically conductive;

d. a first triggerable vacuum arc device in series with said load deviceand operative when rendered conductive to connect said load devicedirectly across said acyclic generator, and;

. a second triggerable vacuum arc device and a capacitor in parallelcircuit relation with said first triggerable vacuum arc device, saidsecond triggerable vacuum arc device being operative when renderedconductive to neutralize the effect of said first triggerable vacuum arcdevice being operative and thereby disconnect said load device from saidacyclic generator.

2. The apparatus of claim 1 wherein said acyclic generator includes aplurality of current generating discs rotatably mounted within asuperconductive field coil and serially connected.

3. The apparatus of claim 2 wherein said discs are divided into a firstgroup which are rotated clockwise by a first rotational motive means anda second group which are rotated counterclockwise by a second rotationalmotive means.

4. The apparatus of claim 1 wherein said first triggered vacuum arcdevice is poled to conduct with a first polarity, and said secondtriggerable vacuum arc device is poled to discharge said capacitor witha second polarity to achieve zero net current through said firsttriggerable vacuum arc device when both of said devices are in theoperative condition.

5. High-energy, short time duration, repetitive pulse apparatus forelectric lamp operation comprising:

a. an acyclic generator adapted to generate an energy change ofin excessof 100,000joules;

b. an electric discharge lamp switchably connected across the outputofsaid acyclic generator;

c. means across said lamp for preionizing the same and rendering itconductive;

d. a first triggerable vacuum arc device connected in series with saidlamp and adapted to connect said lamp across said acyclic generator oncesaid lamp is preionized; and

e. a chargeable capacitor and a second triggerable vacuum arc deviceconnected in parallel circuit relationship with said first triggerablevacuum arc device and operative when actuated to discharge saidcapacitor and neutralize the effects of said first triggerable vacuumare being conductive and disconnect said acyclic generator from saidelectric lamp.

6. The apparatus of claim 5 wherein said acyclic generator includes aplurality of charge accummulating discs rotatably mounted within asuperconducting field coil and serially connected.

7. The apparatus of claim 6 wherein said discs are separated into afirst group which are rotated in a clockwise direction by a firstrotational motive means and a second group are rotated in acounterclockwise direction by a second rotational motive means.

8. The apparatus of claim 5 wherein said first triggered vacuum arcdevice is poled to conduct with a first polarity, and said secondtriggerable vacuum arc device is poled to discharge said capacitor witha second polarity to achieve zero net current through said firsttriggerable vacuum arc device when both of said devices are in theoperative condition.

9. The apparatus of claim 7 wherein said apparatus further includescontrol means to repetitively:

a. preionize said lamp;

b. fire said first triggerable vacuum arc device to discharge a quantityof charge from said acyclic generator through said lamp that is limitedprimarily by the mtemal re-' sistance of said triggerable vacuum arcdevice and said lamp and by contact resistances to cause high-energyenergization of said lamp;

c. deactivate said preionization means;

d. activate said second triggerable vacuum gap device to discharge saidcapacitor and disconnect said acyclic generator from said lamp tothereby extinguish said lamp.

10. The apparatus of claim 9 wherein said control means is operative torender said lamp activated for a period of approximately 250microseconds and to repeat said sequence at a rate of approximately 5such pulses per second.

11. Apparatus for repetitively producing high-energy electric pulses ofvery short time duration and comprising:

a. an acyclic generator adapted to generate and transfer an energy of inexcess of 100,000 joules and including:

a,. means for rotating a first bank of current generating discs uponfirst shaft in a clockwise direction,

a means for rotating a second bank of current generating discs upon asecond shaft in a counterclockwise direction,

a means connecting all of said discs of said banks electrically inseries to provide an electrical output circuit, and

a a superconductive field coil; and b. a load and a commutation means inseries circuit across said output circuit, b said commutation meansincluding a plurality of electric discharge devices for establishing andinterrupting a closed circuit across said output circuit, and

b means for sequentially operating said electron discharge devices todeliver short pulses of high energy to said load.

12. The apparatus of claim 11 wherein said means for connecting saidrotatable discs in series circuit comprises a plurality of stationarydiscs interposed therebetween and electrically connected thereto by aplurality of slidable electrical contacts.

13. The apparatus of claim 12 wherein said stationary discs aremechanically affixed to a cylindrical torque tube adapted to absorbequal and opposite torques from stationary discs associated respectivelywith said bank of clockwise rotating and said bank of counterclockwiserotating discs and transmit zero net torque exterior thereof.

1. Apparatus for repetitively producing high-energy electric pulses ofvery short time duration and comprising: a. an acyclic generator adaptedto generate and transfer a charge of 1,000 joules of energy; b. anelectric discharge load device switchably connected across the output ofsaid acyclic generator; c. means in circuit with said load device forpreionizing said device to render it electrically conductive; d. a firsttriggerable vacuum arc device in series with said load device andoperative when rendered conductive to connect said load device directlyacross said acyclic generator, and; e. a second triggerable vacuum arcdevice and a capacitor in parallel circuit relation with said firsttriggerable vacuum arc device, said second triggerable vacuum arc devicebeing operative when rendered conductive to neutralize the effect ofsaid first triggerable vacuum arc device being operative and therebydisconnect said load device from said acyclic generator.
 2. Theapparatus of claim 1 wherein said acyclic generator includes a pluralityof current generating discs rotatably mounted within a superconductivefield coil and serially connected.
 3. The apparatus of claim 2 whereinsaid discs are divided into a first group which are rotated clockwise bya first rotational motive means and a second group which aRe rotatedcounterclockwise by a second rotational motive means.
 4. The apparatusof claim 1 wherein said first triggered vacuum arc device is poled toconduct with a first polarity, and said second triggerable vacuum arcdevice is poled to discharge said capacitor with a second polarity toachieve zero net current through said first triggerable vacuum arcdevice when both of said devices are in the operative condition. 5.High-energy, short time duration, repetitive pulse apparatus forelectric lamp operation comprising: a. an acyclic generator adapted togenerate an energy change of in excess of 100,000 joules; b. an electricdischarge lamp switchably connected across the output of said acyclicgenerator; c. means across said lamp for preionizing the same andrendering it conductive; d. a first triggerable vacuum arc deviceconnected in series with said lamp and adapted to connect said lampacross said acyclic generator once said lamp is preionized; and e. achargeable capacitor and a second triggerable vacuum arc deviceconnected in parallel circuit relationship with said first triggerablevacuum arc device and operative when actuated to discharge saidcapacitor and neutralize the effects of said first triggerable vacuumarc being conductive and disconnect said acyclic generator from saidelectric lamp.
 6. The apparatus of claim 5 wherein said acyclicgenerator includes a plurality of charge accummulating discs rotatablymounted within a superconducting field coil and serially connected. 7.The apparatus of claim 6 wherein said discs are separated into a firstgroup which are rotated in a clockwise direction by a first rotationalmotive means and a second group are rotated in a counterclockwisedirection by a second rotational motive means.
 8. The apparatus of claim5 wherein said first triggered vacuum arc device is poled to conductwith a first polarity, and said second triggerable vacuum arc device ispoled to discharge said capacitor with a second polarity to achieve zeronet current through said first triggerable vacuum arc device when bothof said devices are in the operative condition.
 9. The apparatus ofclaim 7 wherein said apparatus further includes control means torepetitively: a. preionize said lamp; b. fire said first triggerablevacuum arc device to discharge a quantity of charge from said acyclicgenerator through said lamp that is limited primarily by the internalresistance of said triggerable vacuum arc device and said lamp and bycontact resistances to cause high-energy energization of said lamp; c.deactivate said preionization means; d. activate said second triggerablevacuum gap device to discharge said capacitor and disconnect saidacyclic generator from said lamp to thereby extinguish said lamp. 10.The apparatus of claim 9 wherein said control means is operative torender said lamp activated for a period of approximately 250microseconds and to repeat said sequence at a rate of approximately 5such pulses per second.
 11. Apparatus for repetitively producinghigh-energy electric pulses of very short time duration and comprising:a. an acyclic generator adapted to generate and transfer an energy of inexcess of 100,000 joules and including: a1. means for rotating a firstbank of current generating discs upon first shaft in a clockwisedirection, a2. means for rotating a second bank of current generatingdiscs upon a second shaft in a counterclockwise direction, a3. meansconnecting all of said discs of said banks electrically in series toprovide an electrical output circuit, and a4. a superconductive fieldcoil; and b. a load and a commutation means in series circuit acrosssaid output circuit, b1. said commutation means including a plurality ofelectric discharge devices for establishing and interrupting a closedcircuit across said output circuit, and b2. meanS for sequentiallyoperating said electron discharge devices to deliver short pulses ofhigh energy to said load.
 12. The apparatus of claim 11 wherein saidmeans for connecting said rotatable discs in series circuit comprises aplurality of stationary discs interposed therebetween and electricallyconnected thereto by a plurality of slidable electrical contacts. 13.The apparatus of claim 12 wherein said stationary discs are mechanicallyaffixed to a cylindrical torque tube adapted to absorb equal andopposite torques from stationary discs associated respectively with saidbank of clockwise rotating and said bank of counterclockwise rotatingdiscs and transmit zero net torque exterior thereof.